Nowadays, a hybrid electric vehicle and an electric vehicle are spreading rapidly, and improvement of assembling productivity and downsizing are required for the power conversion apparatus. Generally, as a method for improving assembling productivity and downsizing, modularization of parts is employed. Modularization is carried out for a power semiconductor module and a smoothing capacitor module as described in Patent Literature 1 (JP 2009-219270 A).
Further downsizing is required for a power conversion apparatus for a vehicle, which increases the effect of heat transfer between modules. Therefore, it is required to lower the heat generation of each module.